Alternating current wave production



June 1941- E; PETERSON 2,246,534

ALTERNATING CURRENT WAVE PRODUCTION Eiled June 26, 1940 F/ 8 GAS F'ILL ED PM AVAM 9 I v IL: 7

I A GAS FILLED /5 I OUTPUT INPUT f ru'uso ref 3 W,

I W'" 6 I3 I? W. E10 20 FIG? '5 4o 0-, l- 8 2 4 TIME-MICROSECONDS OUTPU T- M ICROWAT TS .6 .al 2 3 4 s a HARMONIC OUTPUT FREQUENCY MEGACYCLES (INPUT f; 4m) INVENTOR [.PETERSON ATTORNEY Patented June 24, 1941 2,246,534 ALTERNATING cuanng'r WAVE PRODUC- Eugene Peterson, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application June 26, 1940, Serial No. 342,427 8 Claims. (Cl. 172-281) This invention relates to the generation of alternating current waves, and particularly to the generation of a number of waves of different frequency and is abruptly'discharged once during each cycle of the base frequency wave to produce a series of impulses from which the desired harmonics are obtained. While a wide frequency range of harmonics of uniform amplitudes and relatively high power levels is obtainable by the invention of my patent mentioned above, it is desirable for some purposes to obtain an even wider frequency range of such harmonics.

An object of the present invention is to increase the width of the frequency range of harmonics of uniform amplitudes and relatively high power levels which may be obtained from a single wave of given base frequency.

Another object is to increase the number of harmonics of uniform amplitudes and relatively high power levels which may be derived from a single wave of given base frequency.

A further object is to improve the circuit described in my Patent No. 2,174,165, so that the time constant of the impulse timing circuit may be increased to improve the efliciency of operation. 1

These objects are attained in accordance with one aspect of the'present'invention, by a circuit -.35

employing in addition to a first gas-filled electron discharge device of my above-mentioned patent, a second gas-filled electron discharge device so connected with the capacitor-impedance timing circuit in the output of the first device through which the capacitor discharges during a part of each cycle of the given base frequency wave, as to chop off the trailing end of each discharge impulse in response to the first part of the impulse, whereby a wider frequency range of harmonics of uniform amplitudes and relatively high power levels may be obtained from the resulting shortened impulses than from impulses unshortened by the chopping operation.

' through devices These and other objects and features of the invention will be understood from the following detailed description thereof when read in connection with the accompanying drawing in which:

Fig. 1 shows schematically a harmonic producer circuit; and

Figs, 2 and 3 show curves illustrating the results of operation of the circuit of Fig. 1.

Fig. 1 shows an impulse producer or harmonic producer in whichthe alternating current wave source -I of a given fundamental or base frequency f is connected across the pair of input terminals across which is connected the resonant circuit 2, 3, including the condenser 2 and the inductance 3 in series, tuned to the frequency f. The terminals of the inductance 3 are connected through the resistor or resistive impedance '4 across the timing circuit CR including the capacitor 0,5 and the resistor or resistive impedance R,6 in series, the impedance 4 being connected between the capacitor 5 end of the timing circuit 5, 6 and the junction between the condenser 2 and inductance 3. The three-electrode gas-filled electron discharge device I has its anode connected with the capacitor 5 end of the timing cir- The control grid of the device 1 is connectedv through the series current limiting resistance I with the condenser 2 end of the resonant circuit 2, 3 and with one terminal of the source I, the cathode of device 1 being connected with the other terminal of source I. An inductance?! is preferably connected in shunt with impedance 4, as explained in my patent mentioned above;

Another three-electrode gas-filled electron discharge device IO, used as a chopper, has its cathode connected with the junction between the capacitor 5 and impedance 6, its anode being connected with the capacitor 5 end of circuit 5, 6 through the series current limiting resistance H, and its control grid being connected with the impedance 6 end of the circuit 5, 6 through the series current limiting resistance H.

The source of potential l3 in series with the grid circuit of device It, and the source H in series with the grid circuit of device 1, provides the usual negative polarization for the respective grids for blocking the discharge of current 1 and I0 until predetermined control potentials are applied to the grids. The harmonics of the base frequency taken off from the output terminals l5 extending from the terminals of the impedance 6 may be separated in any suitable manner by the use of parallelfllters or tuned circuits (not shown) respectively selective to the different harmonics.

"The operation of the circuit of Fig. 1', without the chopper device ID, will be understood from per second from in my Patent 2,174,165, while the description in my Patent No. 2,174,165. The curve 20, Fig. 2, obtained by an oscillograph from the Fig. 1 circuit with arbitrarily chosen constants but without the device l0, shows how the outpu voltage impulse across impedance 6 varied with respect to "time during a part of each cycle of a base frequency wave of four kilocycles the source I, while current was discharged through the device 1, the capacitor 5 being 500 micromicrofarads, the impedance 6 being a resistance of 300 ohms, resistance 4 being 25,000 ohms, resistance 8 being 50,000 ohms, inductance 9 being 50 millihenries, and the device I being a Western Electric tube D9885'7. The duration of impulse 20- was approximately .73 microsecond.

Considering now the operation of the combination with the device l0, it will be seen that when the charge on capacitor 5 is poled in a direction to discharge through device I, it is also poled properly for a through device I and impedance 6 reduces the negative polarization or produces positive polarization of the grid of device 10. The capacitor 5 starts to discharge through device I, as described the device I is blocked. The source 13 is adjusted to such a value that during the first part of the discharge of the current impulse through device I and impedance 6, the polarization of the grid of device I0 is quickly changed sufficiently to unblock and cause ionization of device l0, thereby producing a relatively low impedance path directly across capacitor..5, thus chopping off the trailing end of the discharge impulse and greatly accelerating the discharge of the capacitor. The adjustment of the sources l3 and made while watching the impulse curve traced by an oscillograph of the electron discharge type. The shortened output voltage impulse resulting from the chopping operation, using arbitrarily chosen constants, is shown by the curve 2 i, Fig. 2, obtained by an oscillograph, the device I0 being of the same type as device I as stated above, the resistance ll being 25 ohms, the resistance l2 being 500 ohms, and the other constants being the same as those mentioned above in connection with curve 20. The arbitrarily chosen constants mentioned above are given merely by way of iilustration of a typical case, and it will be understood that the circuit is not limited thereto but may have a wide range of values to suit the occasion.

It will be seen that the effect of the chopper device I0 is to divert current from the impedance 6, so that the current through the impedance quickly returns to zero and the potential across the output terminals l drops much more abruptiv to zero than in the case of the circuit not using 7 the chopper, the duration of the impulse 2| being about .2 of a microsecond or less thanone-third that'of impulse 20. r

I have found that the output'impulse of shortened duration yields a considerably wider frequency range of harmonics of uniform amplitudes and relatively high power levels, as shown by curve 22, Fig. 3, than in the case of the impulse' unshortened by the chopping operation, the harmonic yield of which is shown by curve 23. The ordinates of curve 23 have been multiplied by a factor of four, in order to provide a ready comparison with the frequency distribution of curve 22. Furthermorawhen the duration of discharge through device l0, and that discharge of current from capacitor 5 It may be conveniently the output impulse is made as nearly as possible equal for the circuits with and without the chopper device It], the shape of the impulse produced by the chopper is such as to yield a much wider frequency range of harmonics of uniform amplitudes and relatively higher power levels by a factor of four, roughly, than the impulse produced without the chopper. Under these circumstances, the timing circuit 5,6 of the harmonicv producer using the chopper may have a time constant which is much larger than that of the circuit 5,6 operating without the chopper. This situation is indicated to some extent by the yield of harmonies shown by curve 22 for a chopper circuit with which the timing circuit had a time constant CR of times Illas compared with the harmonic yield shown by curve 23 for a circuit in which, the time constant CR. was 1.5 times 10- without a chopper. When the time constant of the circuit 5, 5 without the chopper ID was made equal to that with the chopper, the other constants of the circuit remaining the same as above, the amplitudes of the resulting harmonics were no longer uniform but decreased rapidly with increase of frequency, as shown by curve 24, Fig. 3. The circuit 5, 6 when used with the chopper 10, should preferably have a time constant greater than 3 times 10-, as contrasted with a time constant of less thanthis value in cases where the chopper is not used.

It is, of course, to .be understood that variations, substitutions and extensions as desired may be made within the scope of the claims without departing from the spirit of the invention.

What is claimed is:

1. In combination with a harmonic producer employing a gas-filled electron discharge device to control the charge and discharge of a capacitor-impedance circuit in response to an alternating current wave of a given base frequency to produce sharp impulses containing harmonics of said base frequency, means for increasing the frequency range over which harmonics of uniform amplitudes may be obtained by said harmonic producer comprising means including a second gas-filled electron discharge device responsive to the discharge of said capacitor for shortening the duration of said discharge, and means for' taking off harmonics of said base frequency wave from said capacitor-impedance circuit. 7

2. In combination with a harmonic producer employing a gas-filled electron discharge device to control the charge and discharge of a capacitor through an impedance in response to a wave of given base frequency to produce sharp impulses containing harmonics of said base frequency, means for increasing the efficiency of production of harmonics of uniform amplitudes by said harmonic producer, comprising means for shortening the duration of the discharge of said capacitor, said means including a second gasfilled electron discharge device, and means for causing the operation of said second device in timed relation with the operation of said first device, and means for taking oil harmonics of said base frequency wave from said capacitorimpedance circuit.

3. A harmonic producer, including a gas-filled electron discharge device havin an input circuit and an output circuit, a capacitor and a resist ive impedance in series in said output circuit a circuit for charging said capacitor, means responsive to an alternating current wave of a given base frequency for applying said wave t said input circuit to periodically cause ionization base frequency current in said device so as to allow said capacitor to discharge through said deviceand said impedance during a part of each cycle of the applied wave, means for taking off from said output circuit harmonics of said base frequency thereby produced in said output circuit, means including a second gas-filled electron discharge device having its discharge path connected across said capacitor for making the amplitudes of said harmonics more uniform over a wide frequency range, and means responsive to the discharge current of said capacitor through said first device to cause ionization in said second deviceto provide a low impedance discharge path for said capacitor.

4. In an impulse producing circuit, a timing circuit including a capacitor in series with a resistive impedance, a first gas-filled electron discharge device having an anode connected with the capacitor end of-said timing circuit, a cathode connected with the impedance end of said timing circuit, and .a control element, a second gas-filled electron discharge device having an anode connected with the capacitor end of said timing circuit, a cathode connected with the junction between said capacitor and impedance, and a control element connected with the impedance end of said timing circuit, input terminals having connections with said timing circuit and the control element of said first disg charge device, means in said connections for controlling the relative time of response of the anode and control element of said first discharge device to current from said terminals, and means for taking off impulses from said timing circuit in response to predetermined impulses applied to said input terminals.

5. In a harmonic producer, agas-filled electron discharge device having an input circuit and an output circuit, a capacitor and a resistive impedance in series in said output circuit, terminals for applying to said producer a source of periodic current of given base frequency, a charging circuit connecting said terminals with said capacitor-impedance circuit, means responsive to said from said terminals for causing ionization in said device during a part of each cycle of said base low said capacitor to put circuit, a second frequently current to algas-filled electron discharge device having an input circuit including said impedance and an output circuit including said capacitor, means responsive to capacitor discharge current through said first discharge device for causing said second discharge device to ionize and thereby shorten the duration of disdischarge through said outcas timing circuit, a second tion from the anode of said charge of said capacitor, and means to take on harmonics of said base frequency current from the output of said first discharge device.

6. In the harmonic producer of claim 5, a resistive impedance in series with said capacitor and the output circuit of said second discharge device.

7. In an impulse producer, a timing circuit including a capacitor and a resistive impedance in series, a first gas-filled electron discharge device having an anode, a'cathode, and a control element, a connection from said anode to the capacitor end of said timing circuit, said cathode being connected with the impedance end of said gas-filled electron discharge device having an anode, a cathode, and a control element, a resistance-including connecsecond device to the capacitor end of said timing circuit, the cathode of said second device being connected with the junction between the capacitor and impedance of said timing circuit, a resistance-including connection from the control element of said second device to the impedance end of said timing circuit, a pair-of input terminals for said producer, a circuit including a condenser and an inductance in series connected between said terminals and tuned to resonance for a given frequency,

.an impedance-including connection from the junction of the condenser and inductance of said resonant circuit to the capacitor end'of said timing circuit, a connection from the inductance end of said resonant circuit to the impedance end of said timing circuit, a resistance-including connection from the condenser end of said resonant circuit to the control element of said first discharge device, and means for taking off impulses from said timing circuit in response to current of resonant frequency applied to said terminals.

8. In combination with a harmonic producer employing a gas-filled electron discharge device to control the charge and discharge of a capacitor-impedance circuit in response to ,a wave of given base frequency to produce sharp impulses containing harmonics of said base frequency, means including a second gas-filled electron discharge device having its discharge path connected across said capacitor for making the energy distribution of said harmonics more uniform over a wider frequency range, said means being responsive to the discharge of said capacitor to ionize saidsecond device and provide a low impedance discharge path for said capacitor.

, EUGENE PETERSON. 

